Photographic light-sensitive materials are generally composed of light-sensitive photographic emulsion layers and light insensitive layers such as an interlayer, an emulsion protective layer, a filter layer, or an antihalation layer applied, directly or indirectly through a subbing layer, to one side or both sides of the support including, for example, an .alpha.-olefin such as polystyrene or polyethylene, a cellulose ester such as cellulose acetate or nitrocellulose, a polyester such as polyethylene terephthalate or polyethylene napththalate, paper, or a synthetic paper. In light-sensitive materials such as color photographic elements, auxiliary layers such as an antistatic layer, a curl preventing layer, a magnetic recording layer, a barrier layer, a scratch resistant overcoat layer, or a surface lubricant layer, are provided on the back side of the support in order to enhance photographic or physical quality of the photographic light-sensitive materials.
It is always desirable to have a backside protective overcoat that serves as many functions as possible in order to reduce manufacturing complexity and cost. It is also desirable to have such a layer formed by coating and drying from coating compositions based on solvents that are less hazardous to the environment.
Prior art has disclosed the use of a protective overcoat or a "barrier" layer to maintain post-process conductivity of an antistat. Typically such protective overcoats are composed of hydrophobic materials such as cellulose acetates, cellulose acetate butyrates, cellulose acetate propionates, cellulose nitrates, polyacrylates, polymethacrylates, polystyrene, and poly(vinyl acetal).
When such hydrophobic barrier layers are used as an outermost surface layer, deposition of material or "scum" formation on the outermost surface following photographic processing is commonly seen. For example, U.S. Pat. No. 4,735,976 discusses how surfactant from the final photographic processing solution, known as the stabilizer solution, can form a deposit on the outermost surface layer and thereby lead to an objectionable surface haze or scum. Similarly, U.S. Pat. No. 4,582,784 discusses the occurrence of spotted drying unevenness on the outermost surface. Another type of processing scum that is particularly troublesome is hard-water scum. Processing laboratories that are located in hard-water areas are particularly susceptible to this problem. After processing in solutions prepared using hard-water, a white hazy surface scum, sometimes uniform and sometimes more liney and streaky, can be seen on the film. Chemical analysis of the hard-water scum typically reveals hard-water salts of calcium, magnesium, and sodium.
Such surface deposits (contaminates) can impact the physical performance of the element in a variety of ways. For example, large deposits of material on a photographic film lead to readily visible defects on photographic prints or are visible upon display of motion picture film. Alternatively, post-processing debris can influence the ability of a processed film to be overcoated with an ultraviolet curable abrasion resistant layer, as is done in professional photographic processing laboratories employing materials such as PhotoGard, 3M. Finally, processing residue on photographic elements can impact the ability to read magnetically recorded information on a processed film, such as the new Advanced Photographic System films.
Of particular concern is during the handling of photographic materials such as coating, drying, finishing, winding, rewinding, processing, printing, and so on. The surfaces of the photographic material are often harmed by contact friction with the apparatus parts, or scratched by hard debris or objects such as dust, sand, grit, or any other abrasive materials attached to those apparatus. These scratches can deface the image during printing and projecting processes.
Heretofore, there have been various proposals to obtain a physically improved photographic material by increasing the abrasion and scratch resistance of the overcoat layer, or by reducing the contact friction of the photographic material to other surfaces so that it will not be damaged during the manufacturing, exposure, developing, and printing or projecting processes. For example, methods for improving the scratch resistance include adding a certain class of hardener to gelatin; using colloidal silica in the overcoat layer either alone or in combination with a water soluble polymer having a carboxylic acid group; using two overcoat layers, the upper layer containing a colloidal silica and the lower layer containing a polymer latex; and using a composite latex comprising a polymeric acrylic acid ester and/or a polymeric methacrylate acid ester and colloidal silica. Methods for reducing the contact friction include incorporating both a silicone fluid and a surface active agent into the protective overcoat; using a mixture of dimethyl silicone and diphenyl silicone on the backside of the support; incorporating a triphenyl terminated methyl phenyl silicone into the emulsion protective overcoat; using a combination of dimethyl silicone and beta-alanine derived surfactants; using modified sperm oils in the protective overcoat; using liquid organopolysiloxane with methyl and alkyl or aryl, or aralkyl side groups in the protective overcoat; and by using polysiloxane with polyether side chains on the backside of the support.
In recent years, the conditions under which photographic materials are manufactured and utilized have become more severe. This is either because applications of photographic elements have been extended to more harsh conditions such as high humidity and high temperature or because preparation methods have been advanced, including high speed coating, high speed finishing and cutting, and faster processing. Further, the emulsion layers have been progressively thinned. Under these conditions, photographic elements, and materials are more severely scratched and the above-mentioned methods have to be modified, or improved, or optimized for best protection.
Recent patents have described apparatus for scanning and digitizing photographic images. For example, U.S. Pat. Nos. 5,221,975 and 5,255,114 describe a high resolution scanner which is adapted to digitally record an image from a photographic film. The scanner comprises a folded integrating sphere which projects illumination on the film as the film is moved relative to the integrating sphere. Light transmitted through the film is directed to a photodetector by an optical system. It is expected that aforementioned surface scratches and contaminates can significantly influence the ability of the high resolution optical scanner to digitally record images from photographic films.
The foremost objective of the present invention is to provide wax compositions for removing scratches and other defects from the surface of a photographic material in order to improve the quality of photographic prints or projected photographic images or scanned images by an optical scanner in the situation where the surface of the photographic material have become scratched or contaminated.